Mycobacterium tuberculosis, the primary agent of tuberculosis, infects one-third of the world's population and kills 3 million people annually, making it the world's leading cause of death from a single infectious agent. It is a leading cause of disease and death in AIDS patients, particularly in the developing nations of the world. The rapid global emergence of strains resistant to the major antibiotics used to treat tuberculosis poses a serious threat to public health. The highest priority in the fight against tuberculosis is the development of a vaccine that is more efficacious than the current vaccine - BCG. A vaccine more potent than BCG would have an impact on human health greater than virtually any other conceivable development in the fight against infectious diseases. Studies from this laboratory completed under the current grant established the importance of major extracellular proteins of M. tuberculosis in inducing both cell-mediated and protective immunity in the guinea pig model of pulmonary tuberculosis, a highly susceptible species that develops disease remarkably similar to human tuberculosis. Studies under the current grant also succeeded in developing technology for high level expression and secretion in native form of major M. tuberculosis extracellular proteins in a nonpathogenic rapidly growing heterologous host, allowing isolation and purification of 100 mg quantities of recombinant M. tuberculosis extracellular proteins for vaccine studies. In this grant application, we seek to build on the knowledge and experience gained in previous studies to develop a vaccine more potent than BCG in the highly relevant guinea pig model. We seek to develop and test live recombinant vaccines including recombinant BCG expressing major M. tuberculosis extracellular and cell-associated proteins and new non-live particulate vaccines formulated as liposomes and microspheres.